Updated | Many turn to e-cigarettes to help themselves wean off nicotine by moving to lower and lower doses, or as a "safer alternative" to tobacco. However, a study published in the Journal of the American Heart Association found puffing just one e-cigarette with nicotine can damage the heart in nonsmokers.

A team of researchers at the University of California, Los Angeles, looked at 33 healthy nonsmokers who came to the lab on three different days separated by at least four weeks for three different e-cigarette exposures in random order to determine its effect on the adrenaline levels in the heart. The participants were asked to puff an e-cigarette with nicotine one day, an e-cigarette without nicotine (same flavoring and solvents) another day, and puff on an empty e-cigarette as a control.

Dr. Holly R. Middlekauff, senior study author and a cardiologist at UCLA, and her colleagues found participants developed a pattern of abnormal “heart rate variability” (HRV), which is indicative of increased heart adrenaline levels after using the e-cigarette with nicotine only. These increased adrenaline levels were attributable to the inhaled nicotine and not the non-nicotine components in the e-cigarette aerosol. Nevertheless, the researchers did not find increased oxidative stress because they only looked at one marker, therefore this warrants further testing to support this finding.

This does not take away from the potential harm e-cigarettes can do to the hearts of nonsmokers.

"Importantly, and of concern, this abnormal pattern of HRV detected after using the e-cigarette with nicotine was the same pattern associated with increased cardiac risk in multiple populations with and without known cardiac disease," Middlekauff told Newsweek.

Although the non-nicotine components did not lead to an increase in adrenaline levels, Middlekauff stressed these e-cigarettes cause changes in a person's HRV that mimic the same HRV pattern linked to cardiac risk. This challenges the belief that nicotine is benign and without significant risk.

Several recent studies have slowly helped uncover the health risks of e-cigarettes. For example, a study last year found vapor from e-cigarettes contain propylene glycol and glycerin, two previously unidentified chemicals that can cause cancer and used to make artificial smoke — and the levels of these harmful chemicals vary between e-cigarettes. Vaporizers released a total of 31 harmful chemicals, including formaldehyde, acetaldehyde, and acrolein, which are all carcinogens or respiratory irritants, The Vergereports.

The amount of chemicals was contingent on the temperature at which the liquids were vaporized by the device's heating coil. The higher the temperature inside the coil, the more chemicals that were emitted. Also, the longer the e-cig is being used, the more chemicals released because chemical residue builds up on or near the heating coal.

Moreover, inhaled nicotine that comes from e-cigarettes, traditional cigarettes and other tobacco products, like hookah, rapidly enter the bloodstream and the brain, stimulating nerves that carry the adrenaline to the adrenal gland to release adrenaline, Reuter Health reports.

However, Middlekauff explained, "This happens to a lesser extent with nicotine delivered by patches and gum, since with these delivery systems, the nicotine levels increase much more slowly, and remain at lower levels, compared to inhaled nicotine delivered by cigarettes."

She emphasized that if you currently smoke tobacco cigarettes, switch to e-cigarettes for a better choice, and then try to get off e-cigarettes as soon as possible.

The study also serves as a wake-up call for nonsmokers who decide to smoke "just once." Non-e-cigarette users and nontobacco cigarette smokers experience changes in adrenaline levels in the heart, which is a cause for concern. "If you do not smoke already, do not start using e-cigarettes. They are not harmless," Middlekauff warned.

Correction: September 21, 2017

An earlier version of this article misstated one puff of an e-cigarette with nicotine can damage the heart in nonsmokers. Puffing on just one e-cigarette can damage the heart in nonsmokers.